You better buy that 600 or you'll just be back to the store keep buying more tools, at least with the 600 you'll have enough blower to keep you going a while (plus you'll be broke too but that's another story) seriously it is one bad ass machine it is not a question with the 600, you will never again wonder if it's enough.
And it may not be the last blower you'll ever buy, but what if it is, at least it will always do the job.

One more thing...
Take good care of it, they're made to last 20 years.